Process and apparatus for the electrolytic decomposition of alkaline salts.



J. GREENWOOD.

PROCESS AND APPARATUS FOR TH E ELECTROLYTIC DECOMPOSITION 0F ALKALINE SALTS,

APPLICATION FILED NOV. 22, 1909.

Patented Feb. 21, 1911.

4 SHEETS-SHEET l. b N

J. GREENWOOD.

E ELECTROLYTIC DEGOMPOSITIO APPLICATION FILED NOV. 22, I909.

PROCESS AND APPARATUS FOR TH N 0]? ALKALINE SALTS.

Patented Feb. 21, 1911.

4 SHEETS-SHEET 2.

J. GREENWOOD. PROCESS AND APPARATUS FOR THE ELECTROLYTIC DECOMPOSITION 0F ALKALINE SALTS. APPLICATION FILED NOV. 22, 1909.

984,905. Patented Feb. 21, 1911.

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6 l a Z 2 Z '1 Z V-JL z v2 k\L A E i I J. GREENWOOD. PROCESS AND APPARATUS FOR THE ELECTROLYTIC DECOMPOSITION 0F ALKALINE SALTS. APPLICATION FILED NOV. 22, 1909.

984,905. Patented Feb. 21, 1911.

4 SHEETS-SHEET 4.

To all whom 'it may concern:

UNITED STATES. PATENT oFFc.

JAMEs GREENWOOD, or LONDON, ENGLAND.

PROCESS AND AIPYARATUS FOR THE ELECTROLYTIC DECOMPOSITION ALKALINE SALTS.

Specification of Letters Patent.-

Patented Feb. 21, 1911.

Application filed November 22, 1909. Serial No. 529,442.

Be it known that I, JAMES GREENWOOD, a subject of the King of England, residing at, London, England, have invented a certain new and useful Improved Process and Apparatus for the Electrolytic Decomposition of Alkaline Salts, of which the following is a specification.

This invention relates to improvements in the electrolytic decomposition ofv alkaline salts by the diaphragm method, chiefly for the production of caustic soda and caustic potash from sodium chlorid and potassium chlorid respectively; the object. being to produce an electrolytic system which will work efliciently and economically even under the most variable conditions of electrical supply. To this end the method and apparatus are so devised as to enable the electrical resistance,

the rate of flow of electrolyte, the percolation of electrolyte through the diaphragm and other factors to be readily controlled, as may be required.

According to this invention the resistance of an electrolytic cell is tontrolled in accord anee with the current density employed by hermetically closing the cathode section except for the diaphragm and by reducing more or less the pressure in the cathode section, which is normally practically empty to regulate the rate of percolation of the elec trolyte through the diaphragm.

A feature of this invention consists in the use of a cathode section hermetically closed and connected to a suction pump by means of which the necessary reduction of pressure can be effected and by which also the caustic liquor mixed with alkaline chlorid solution may be withdrawn from the cathode section.

According to this invention the anode, diaphragm, cathode, and easing of the cathode section are preferably in the form of concentric cones or V-shaped rectangular vessels, though they maybe constructed'in any suitable pyramidal form. Preferably the apparatus comprises a series of superimposed and concentric cells so arranged that the electrolyte flows from a hollow anode to the corresponding anode section (that is, the space between the hollow anode and the adjacent diaphragm member =of the correspondin cathode), thence to the next hollow ano e and into the corresponding anode section and so on in cascade.

With such an arrangement it is possible to regulate the flow of liquor into the first hollow anode and thereby through the whole apparatus, in accordance with the current density.

One method of carrying this invention into effect will now be described with reference to the accompanying drawings.

Figure l is a side elevation partly in section. Fig. 2 is a plan the cover of the apparatus and the uppermost anode being re- .moved. Fig. 3 shows on an enlarged scale one of the cathode sections. Fig. 4 shows a side elevation partly in section of a modified 'form of apparatus, and Fig. 5 is an end elevation of the modified apparatus part of the casing being removed.

Like letters indicate like parts throughout the drawings.

The anode section of the first or upper cell contains a hollow anode A in the form of an inverted cone, constructed of ferrosilicon alloy or other material which effectually resists the 'electrolytic action at the anode. This anode has an outlet B at its apex.

The cathode section which is located immediately under the anode A is constructed follows :The inner member C consists of a porous vessel or diaphragm and the outer member C is constructed from ebonite or other suitable material, and is provided with an internal annular projection C Outside the diaphragm is a layer of asbestos cloth C surrounded by a layer of copper gauze 6*, the latter forming the cathode proper. The application of the cathode in the form of metallic gauze directly to the'outer surface of the diaphragm is a well-known form of' construction. A copper ring I) surrounds the top of the cathode and is metallically, secured thereto, preferably by soldering. The ring D 1T5 arranged to rest on the annular projection C of the outer casing C and to support the diaphragm C by a flange C on the latter resting on the top of the ring D. Copper bolts H are secured to the ring D and project above the edge of the cathode section. The space surrounding the bolt and above the ring D of the cathode section is filled in with any suitable cement. The bolts H are further provided with nuts D which 3 D are secured at intervals around the outer surface of the outer casing C" and form distance pieces and supports for the cathode section when in position in the underlying anode section as shown in Fig. 1. tube E is provided in each cathode section the tubes in being allconnected to a main pipe E the latter being in communication with a vacuum effect apparatus or pump.

Anode and cathode sections are arranged concentrically one below the other to the required number as illustrated in Fig. 1.

The apparatus is incased in a porcelain enameled iron 'or other suitable vessel or casing F mounted in a bed plate F of slate or other non-conducting material and being closed at the top by' a cover F Through this cover a tube F 3 conveys the alkaline salt solution which is to be decomposed to the upper anode section and another tube F is provided to carry off the chlorin gas which is evolved during the process.

Three columns G are supported in the base plate and are provided with projections G which engage corresponding projections A formed on the anode sections, thereby supporting the sections in place. These columns G form the positive terminals of the apparatus and in order to secure good electrical contact between the columns and the anodes, packing Gr composed of sheets of soft lead is inserted between the projections A and the projections G.

Separate and insulated conductors H are carried through the bed plate F and are connected separately to each of the extended copper bolts H which form electrical contact by means of the copper ring D with the cathode O", whichform the negative terminals of the apparatus. These conductors are carried to a specially constructed terminal outside the apparatus deslgned so that each cell can be tested separately as to its electrical condition. outlet J is provided in'the bed plate F i hereby the elec trolyte finallypasses away from the bottom section. v

Figs. 4 and 5 illustrate a modified construction of apparatus. In place of the sec tions having conical formation they are constructed in V-form, that is to say,-the apparatus is now provided with side walls K of slate, ebonite or other suitable material, '55

An ebonite plates to the electrical conductor G which leads to the positive terminal of the electrical supply.

The arrangement and operation of the apparatus is with the exception ofthe details described above similar to that of the conical construction.

The process of decomposing alkaline salts in the apparatus described is as follows: The solution of alkaline chlorid is introduced into the'upper anode A through the conduit F which maybe controlled by a suitable valve. connected in cascade this valve can be operated to regulate the flow of the electrolyte liquor through the whole apparatus in accordance with the current density so that the electrolyte when leaving the cell can be maintained at a practically constant specific gravity L and-so that the temperature may be regulated. The electrolyte having passed from the bottom of each hollow anode A into the anode section ascends therein and is subjected to the action of the electric current passing from the anode through the diaphragm C to the cathode C and at the same time the electrolyte percolates through the diaphragm, the rate of percolation being regulated by the vacuumdn the cathode section according to the current density employed and caustic alkaline liquor is pro duced in the cathode section together with a certain proportion of alkali chlorid. This caustic alkaline liquor is removed through the suction conduit E. By varying the degree of vacuum it is possible to regulate-in the most exact manner the rate of percolation of the electrolyte through the diaphragm, and by this means the resistance of the cell can be regulated according to the variable current density. Thus when -the current density is high, the vacuum in the cathode section is increased to a maximum, so as to permit a. greaterpercolation through the diaphragm, and, thereby produce a less resistance; and when the current density is low the vacuum is reduced correspondingly As the anode sections are to diminish the percolation through the diaphragm. By this regulation of the percolamaintained at a, constant strength and quality. H

At electric power generating stations, the power actually utilized is generally less than 30% of the total generating capacity. The process and apparatus according to this invention are especially suitable for utilizing the variable surplus electric power amounting to over 70% of the total generating capacity. For this particular purpose, it is absolutely necessary that the electrolytic apparatus should work efliciently and economically even under the most variable conditions of electrical supply. At the same time it is desirable to maintain the voltage of the electrode and diaphragm surface within very small compass. This arrangement facilitates the automatic flow of the electrolyte, from cell to cell, by gravity, and at the same time allows the chlorin evolved in the anode section to pass away t'reely. The partially exhausted electrolyte after passing through the series of .cells is pumped back to be resaturated with the'alkali salt. The cost of this apparatus and erection is greatly reduced by thismethod of construction, which can also be easily enlarged atnany time, by

increasing the number of cells in each ap-- paratus as may be required.

The invention has "been described in its application to the production of caustic alkali from alkali chlorid but it is obvious that the process and Iapparatus may be adapted to the manufacture or production of other chemical products, the details of construction being capable ofmodification without departing from the spirit of the invention.

What I claim as my invention and desire to secure by Letters Patent is 1. The hereinbefore described improvement in the method of electrolytically decomposing alkaline salts by the diaphragm process Which consists in producing a partial vacuum in the cathode section.

2. The hereinbefore described improvement in the method of electrolytically decomposing alkaline salts by the diaphragm process which consists in,producing a par tial vacuum in the cathode section and maintaining said cathode section normally practically empty.

3. The hereinbefore described improvement in the method of electrolytically decomposing alkaline salts by the diaphragm process which consists in closing the cathode section, producing a partial vacuum in said cathode section and maintaining it normally practically empty.

4. In the electrolytic decomposition of alkaline salts by the diaphragm process, varying the rate of percolation of the electrolyte through the diaphragm by closing the'cathode section which is normally practically empty andproducing apartial vacuum therein. I

5.' In the electrolytic decomposition of alkaline salts by the diaphragm process, the method of varying the resistance in accordance with the current density consisting in closing the cathode section and producing a partial vacuum in such cathode section to alter the rate of percolation of the electrolyte through the diaphragm.

6. In the electrolytic decomposition of alkaline salts by the diaphragm process, the herein described improvement consisting. in closing the cathode section, producing apartial vacuum in said section, and withdrawingthe, caustic liquor by suction from-the bottom of the cathode section;

7. In apparatus of the diaphragm type the combination with a closed cathode section, of a suction pump connected with the interior of said sectio 8. Apparatus for the electrolytic'decomposition of alkaline salts by the diaphragm process in which the anode, diaphragm, cathode and easing of the cathode section are in the form of concentric pyramidal formations. I

9. In apparatus for the decomposition of alkaline salts by the diaphragm process, the

combination with a'cathode including a hollow diaphragm, of a hollow cone or pyramid-shaped anode extending into and providing between its outer surface and the cathode diaphragm a chamber through which electrolyte may flow, the anode hav-- ing at its lower end an outlet communicat ing with said chamber;-

10. Apparatus of the kind described,hav-

ing a series of superimposed and concentric cells so arranged that the" electrolyte flows from the hollow anode to the corresponding anode section, thence to the next hollow' anode and into the corresponding anode section and so on.

11. The herein described method of decomposing alkaline salts by electrolysis consisting in causing the liquor to pass through a series of superimposed and concentric cells, each comprising a hollow anode and a cathode regulating the flow of liquor into the first hollow anode, and therefore through the whole apparatus in accordance with the current density. v

12. In apparatus of the kind described,

the employment of cathode sections, each consisting of an outer pyramidal casing of suitable material, an inner pyramidal member including a porous'diaphragm, a metal- X 14. In an apparatus of thecharacter described, the combination ofa hollow anode, a cathode section adapted. to receive the name to this specification inthe presence of anode and comprising an inner 'porous' two subscribing witnesses.

diaphragm and an outer shell forming an JAMES GREENWOOD. inclosed chamber about the diaphragm and Vitnesses:

anode, and means for creating a partial PERCY HEWITT vacuum insaid chamber of the cathode. l H. D. JAMEsoN.

- In testimony whereof I have signed my 

